How Central AC Systems Work

The Refrigeration Cycle

  1. Using electricity as its power source, the refrigerant flows through a closed system of refrigeration lines between the indoor unit and the outside unit.
  2. Warm air from the inside of your house is pulled into ductwork by a motorized fan.
  3. The refrigerant is pumped from the exterior compressor coil to the interior evaporator coil, where it absorbs the heat from the inside air.
  4. This cooled air is then pushed through connecting ducts to vents throughout the home, lowering the interior temperature.
  5. The refrigeration cycle continues again, providing a consistent method to keep you cool.

Parts of a Central AC System

A typical central air conditioning system is a two-part or split system that includes:

  • The outdoor unit – Contains the condenser coil, compressor, electrical components, and a fan.
  • Evaporator coil – Which is usually installed on top of the gas furnace inside the home.
  • Refrigerant – The substance in the refrigeration lines that transfers heat into or out of an interior space. It is circulated through the indoor and outdoor unit.
  • Ductwork – A network of metal, fiberboard or flexible material that serves as the air tunnels to deliver conditioned air to the various spaces inside your home.
  • A thermostat or control system – A wall mounted device that monitors and controls the output of your conditioned air.


  • Indoor comfort during warm weather – Central air conditioning helps keep your home cool and reduces humidity levels.
  • Cleaner air – As your central air conditioning system draws air out of various rooms in the house through return air ducts, the air is pulled through an air filter, which removes airborne particles such as dust and lint. Sophisticated filters may remove microscopic pollutants, as well. The filtered air is then routed to air supply duct-work that carries it back to rooms.
  • Quieter operation – Because the compressor-bearing unit is located outside the home, the indoor noise level from its operation is much lower than that of a free-standing air conditioning unit.

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